[PATCH] cleanup-adc-s3c2410_ts.patch

Andy Green andy at openmoko.com
Thu Nov 27 10:35:50 CET 2008

Hash: SHA1

Somebody in the thread at some point said:

| In this case the median filter doesn't help much (and you'll notice
| that the erratic clicks are usually drawn in the middle of the
| screen).

Also the Median filter doesn't issue anything useful until it is full,
the problem with "light" clicks aside from whatever coordinate error
they bring with them is they might not have a very long down duration
and so not a lot of coordinate samples.

| This is a real example of what happens in this case. This is the
| buffer that the median filter has for one of the coordinates (Let's
| say X):
| tsfm->sort[...] =  {288  293  302  302  309  311  316  320  324  445
| 505  516  529  530 539  543  570  588  603  604  722  750  762  764
| 783  810  827  848 865  893  893}
| I guess we should discard this point.


| I tried the variance (standard deviation ^ 2 actually) and a threshold
| and it worked well in the initial tests.
| I'll check more in this direction. An[d]y also has some patches that
| check the pressure of the stylus but he didn't manage to normalize the
| results across the screen [1]. I think we could get away with some
| statistics. There are some tips [2] also to check.

OK.  The only thing that bothers me a bit about spending a lot of time
on this is that I don't think it will apply to GTA03.  There is a little
chip that services the touchscreen there and I guess it has already
prefiltered what it sends out since it is on low speed i2c interface.
Taking a few days to get it straightened out sounds like the right way
rather than weeks to get it perfect.

- -Andy
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